In recent years, regulations imposed on an electromagnetic wave generated from an electric product have been increasingly strict due to radio disturbances inflicting various precision mechanical devices, measuring devices, and digital devices and adverse influences on human bodies. Therefore, the emission of an electromagnetic wave has been legally controlled, for example, by the VCCI (Voluntary Control Council for Interference by data processing equipment electronic office machine). In a PDP which emits a particularly strong electromagnetic wave from an image display unit out of the device, a light-transmitting electromagnetic-wave shielding plate is combined with a plate having another function, such as antireflection and near infrared ray shielding, and the resulting plate is directly bonded to the image display unit as a front-face filter or is bonded to a transparent substrate formed from glass, plastic, or the like, used for the front-face filter, and then the substrate is placed on the image display unit. Thus, the electromagnetic wave can be shielded so as to observe the regulation.
Conventionally, as the light-transmitting electromagnetic-wave shielding plate, a product is proposed, as shown in FIG. 2, in which a patterned conductive metal layer is provided on a transparent substrate 1 by photolithography (d), in such a manner that a metal layer 3, such as a copper foil, is laminated on the transparent substrate 1 with an adhesive layer 2 interposed therebetween (a), a resist film 6 is bonded thereto, and exposure, development (b), etching (c), and resist stripping is performed (d) (Patent Document 1).
As another method of forming the patterned conductive metal layer on the transparent substrate, a method has been proposed, in which an etching resist pattern is formed by a screen printing method or an offset printing method, the conductive metal layer is thereafter etched, and the resist is finally stripped (Patent Documents 2 and 3).
However, a photolithography method for manufacturing the light-transmitting electromagnetic-wave shielding plate using the conductive metal layer laminated on the transparent substrate can complete the formation of a thin-line pattern capable of having an electromagnetic-wave shielding property and a favorable light-transmitting property without any problem. On the other hand, it is necessary to use a copper foil whose one surface or both surfaces are subjected to black oxidation as the conductive metal layer in order to prevent the deterioration of an image quality such as contrast, and thus it is disadvantageously a factor for cost increase. Further, the photolithography includes complicated long processes, and therefore the photolithography can not satisfy cost reduction demanded by the market. There has been also proposed a process in which a black resist layer is laminated on the patterned conductive metal layer, and is not stripped but is left thereon in order to satisfy the electromagnetic-wave shielding property and the visibility of a display screen (Patent Document 4). This process, however, employs the photolithography after all, which also failed to satisfy the cost reduction demanded by the market.
In accordance with a method of forming an etching pattern of the light-transmitting electromagnetic-wave shielding plate by the screen printing method or the offset printing method, a simple device and process can be utilized, and the black resin layer is directly formed on the conductive metal layer having a metallic luster that impedes the contrast performance, and therefore a glittering impression can be controlled. Accordingly, the method can meet the cost reduction demanded by the market. However, in these printing methods, it is difficult to print a fine-pitch line width and to form a pattern with a thin-line of 20 μm or less, which is preferable in terms of the non-visibility of a mesh pattern. Further, the electromagnetic-wave shielding plate thereby obtained is not satisfactory in terms of the light-transmitting property.    Patent Document 1: Japanese Patent Publication No. 3388682    Patent Document 2: Japanese Unexamined Patent Publication No. 2000-315890    Patent Document 3: Japanese Unexamined Patent Publication No. 2000-323889    Patent Document 4: Japanese Unexamined Patent Publication No. H09-293989